In the manufacture of LEDs, especially flip-chip designs, it is advantageous to produce contacts that are both electrically conductive (to provide current to the device) as well as reflective (to allow photons to bounce away from the device). Deposition techniques are used for the formation of these contacts, and the deposition process is often well controlled for the deposition of high quality metals films. Furthermore, conditions are established and/or controlled so as to deposit materials (e.g., metals) in precise composition and thicknesses. It is known that some metal-semiconductor contacts exhibit high resistance (e.g., after deposition) and some properties of the metal-semiconductor contacts are improved in an annealing step (e.g., to increase electrical conductivity). Some legacy techniques go to great lengths to eliminate the presence of oxygen in both the deposition and the annealing steps (e.g., since oxygen can cause a decrease in reflectivity due to oxidation of the contact material). In some legacy cases, a thin layer of Ni or other oxygen gettering material is embedded in the Ag in the hope that it may reduce the oxidation of the Ag. These legacy approaches fail to recognize that oxygen must be present in certain concentrations in order to produce a highly electrically conductive contact. Moreover, legacy techniques fail to teach how to control the oxygen concentration through the range of processing steps. Additionally, legacy techniques fail to account for desirable effects of the presence of oxygen during the processing of metal contacts to allow for high electrical conductivity.
What is needed is a technique or techniques that allow for precise control of the content (e.g., concentration) of oxygen during the processing of the metal contacts in concentrations high enough so as to maintain high electrical conductivity, yet low enough so as to avoid a decrease in reflectivity due to oxidation of the contacts. Therefore, there is a need for improved approaches.